1. Field of the Invention
The present invention relates to a rapid prototyping method using selective infiltration manufacturing process. More particularly, the present invention relates to a rapid prototyping method, which infiltrates molten material between preheated powder particles and manufactures prototypes and molds.
2. Description of the Conventional Art
Conventional rapid prototyping methods fall into two big categories. One method is the curing method, in which liquid state material is scanned by laser beam. The other method is to put solid powder materials or sheet materials together for desired shapes.
One of curing methods is stereolithography (3D systems Co.), in which liquid state photo-polymer is selectively scanned by laser beam and solidified layers are accumulated. Two implementations of the stereolithography are available. One implementation is to scan the laser beam locally (3D systems Co., Quadrax Co., and Sony Co.) and the other is to scan the whole layer using ultra-violet light lamps (Cubital company and Light Scuipting Co.).
However, solidified photo-polymers are shrunk and therefore distortions are caused. In addition, if products have overhangs, the supports are required in order to keep photo-polymers from falling down. Because polymers are used as materials, the degree of strength of final products is decreased and therefore utility of the products is restricted.
Selective Laser Sintering method (DTM Co.) and three dimension printing methods (MIT, Soligen Co., ProMetal Co. and Z Corp.) employ powder materials. The Selective laser sintering method spreads plastic powder materials and then scans laser beam to combine the powders. The Selective laser sintering method is used to manufacture metal products and molds with the help of metal powder coated on plastics. However, for manufacturing metal products and molds, plastics already coated on the metal powders must be removed and then sintering process is required to combine metal powders. Also, a process like copper infiltration must be done at the end of the whole process to fill the gaps between metal powders. This process usually causes heat deformation of final products and therefore accuracy gets severely deteriorated.
In three dimension printing method, liquid state binders are applied to the surface of the spread powder. Using the three dimension printing method, ceramic shells for investment casting can be directly manufactured. Powders whose basic component is starch can be used in the method. However, post-processing is necessary to increase the density and intensity of final products and therefore shrinkage of the final products due to heat deformation is caused.
In Laminated Object Manufacturing method (Helisys Co.), heated rollers glue thin sheet-type papers and lasers cut them. This process is repeated. This laminated object manufacturing method has advantages in that papers are used as a main material and therefore overall costs are relatively low. But it takes long time to decube the desired part from the paper box. Let's suppose that a product with spherical shape needs to be manufactured by the laminated object manufacturing method. In the middle of the process, papers are to be cut and accumulated. Finally, it is going to take long time to pull out the final product because of remaining of papers, which surround the final product of spherical shape. Now, thanks to recently developed plastic thin material, there are ways to manufacture products of plastics by the laminated object manufacturing method. However, it has same drawbacks as the case of products of papers.
In Fused Deposition Modeling method (Stratasys Co.), filament shape plastic materials are passed through nozzles, which have similar shape of extrusion molds. However, the surface of the final product manufactured by this method is rough because filament shape materials are used.
In recently commercialized Laser Engineered Net Shaping (Sandia National Lab., Optomec Co.) method, metal substrate is locally heated and small melt pool is made. Then, metal powders are dropped into the small melt pool. While the final product is being solidified at the final stage, shape distortion may occur because metal material is completely melted in the process. Also, products with overhangs and cantilevers cannot be manufactured by the LENS method by the same reason.
In Shape Deposition Manufacturing (Stanford University and Carnegie Mellon University) method, metal deposition and CNC machine processing are employed. After metal material is deposited, it is processed to have desired thickness and boundary shape by multi-axis CNC milling machine. Then, the remaining portion of the same layer is filled with other metal materials and CNC milling process is applied again to deposit another layer. After the processes of one layer are finished, shot peening operation is performed to eliminate residual stress. The main drawback of the SDM method is that it takes relatively long time to manufacture products.